Plastic impregnated fabric material and method for making same



Oct. 16, 1956 p FRIEDER ETAL 2,766,453

PLASTIC IMPREGNATED FABRIC MATERIAL AND METHOD FOR MAKING SAME FiledMarch 25, 1954 United States Patent-O PLASTIC IM'PREGNATED FABRIC ANDMETHOD FOR MAKING SAME Leonard P. Frieder, Great Neck, and-Walter S.Finken, Brooklyn, N. Y.; said :Finken assignor tosaid Frieder Originalapplication December 21, 1950, Serial No. 201,904, now Patent No.2,739,309,.dated March 27., 1956. Divided and this application Marci125, 195% Serial No. 418,585!

1 Claim. (Cl. 2-3) designed for aviators and the like, where-thecircumstances of the wearer may subject him to severe 'blows about thehead. For example, in high speed aircraft, rapid turns, dives andotherusual or unusual operations often throw the pilot or passenger againstadjacent structural parts of the aircraft with considerable force; -'inconsequence a protective helmet is practically a necessity for personnelunder such conditions, toprotect the skull from injury. Since the helmetmust often be worn for long periods of time, it should be as light inweight and as comfortable as possible. Indeed lightnessof weight is aparticularly important feature, since the same accelerations anddecelerations which tend to throw the wearers head about will likewisetend to displace a heavy helmet relative to his head, putting. extrapressures on his head in an uncomfortable and tiring manner even withoutimpact of external objects. 0

A primary object of the present invention isto provide an improvedimpact resisting material. A further object is to provide such amaterial which is capable of being formed into a shell structure for aprotective helmet.

Another object. is to provide a helmet structure having an improved,light but exceptionally strong shell, as of composite fibrous andplastic ma-terial,. stronglyresistant to shattering or fracture. Amore'speoific object is to provide an improved structural sheet orplate-like material, adapted for embodiment in helmet-shells or othervessels, containers or walls, which is light in weight, durable, andcharacterizedsby the. strength of Efibrously bonded plastic composition,whilehighly resistant to cracking or breaking and specifically free ofany grain or lines of r y cleavag Aa illsfl irther objec is :to providesuch structure or structural; materi al, -pecu1iarly suited for helmetshells as wellasforother uses,..which may be integrally arranged to havedifferent -=.values:.of

weight and strength at various selected. localities.v

The foregoing and other objects of the inventionpre attained byproviding a larninatedstructure, -i-ncludi-ng outer layers of thicklyfelted material and an inner layer of fluffed fibrous, felted mat incontact with an open weave fabric sheet so that the flufr'ed fibrousmaterial works through the openings in the woven sheet. All the layersare impregnated with plastic material in liquid form by known proceduresand the plastic material is then cured by suitable heat and pressuretreatment.

Other objects and advantages of the invention will become apparent froma consideration of the following specification, claim and drawing.

In the drawing:

Fig 1 is a front ,elevational view of the helmet shell constructed ofmaterial embodyingthe invention;

Fig. 2 is an enlarged View .of a portion .of the helmet shell body, withsuccessive layers or parts of the con.- stituent materials broken awayto.,-illustrate the method of lamination or assembly of those materialand Fig. 3 is greatly enlarged sectional view taken on the line Ill-4H1,of Fig. 2 showing ,the, structure of the ,shell in cross-section.

Referring to Fig. 1, there .is shown a shell 20"for ;a protectivehelmet. The shell 20' includes .r-ig'id depending ,flaps .21 at thesides which are somewhat-hulged-out for accommodation of earphones orsimilar instruments. The. bottom edge of the helmet is lower .at the.rear 2.4a than at the front 24b, thereby. providing a skirt likeportion :to protect the base ofthe wearers skull. The, entire lower edgeof the helmet may be embedded in a pro tective head of rubber or othersimilar resilientvmaterial.

The. helmet shell 20 itself, for example as shown in Fig. 1, ispreferably constructed of an essentially. rigid but very tough andstrong material having a constitution such as illustrated in Figs.12.:and 3. This material is constructed of a plurality .of sheets,originally highly flexible, which are superposed in layers andimpregnated withanappropriate composition or the like, as .willnowbedescribed.

Thus in manufacturing the plate-like composition, a layer 1300fpreformed, felted material is first provided. On it is disposed aflutfed, fibrous, felted ma-t 1132 of high. permeability overlaidby afabric 134,of'very open weave, the opposite sidev of the compositestructure being completed bywa further layer 13-6.,of felted,fibrous-;rnaterial which maybe similar' to the layer 130. The sheets ormats 130, 136 are each a ,relativ'elythin feltedmaterial consisting ofirregularly laid fibers appropriately inter- ;meshed but only. veryslightly bonded (by adhesive ma- .terialor-the like), so that-such matconstitutesa thin, highlyfiexi'b-le and :highly porous felt, the ,fibersbeing most; advantageously glass fiber, oralternatively asbestos,:mineral wool, or synthetic substances such as rayon or nylon, .or. evencotton, .woolor other naturalfibers.

The layer. or mass 132- consists of a slightlyfeltedmat of. relativelyloosefibers which have been flulfedhpand which are essentially notbonded together, exceptq'by their mutual interlacing. The Woven netorlfablj c 134 which may have a mesh aslarge as inchor. so, is areasonablystrong=buthighlyporous sheet. The fibrous composition ofsboththe ,fluffed mass -132-and the Woven fabric 134 is of suitable nature,such as the materials named above for the rnatlayers 1130, 136. Asstated the :layers 13!), 136 are prefelted, rolled mats, ,i. e. thinfelted sheets which have been passed between rolls but which arenevertheless highly porous.

In preparing ,theassembly toconstitute an essentially monolithic sheetor.,pla t e-like material, the woven reinforcement 13.4 and fiufifedlayer 113. are assembled ,to-

.gether, ason a suitableflat surface or on a contoured form, andareimpregnated with a bonding :fluid, i. e. preferably to the pointof..at least as fill-1.011438 these m ater'ialswill'hold. .Thessemblypflayers113g, 13 41 then covered on opposite sides by the mats130, 136; indeed if desired, the materials 132, 134 may be laid on oneor the other of the mats 130, 136 before the bonding fluid is applied tothe inside materials 132, 134.

After the second of the mats 130, 136 has been disposed in place, theentire assembly is subjected to considerable pressure, for example byholding it between congruent male and female dies or like surfaces whichPatented Oct. 16, 1956 'dium employed may be have the shape of thehelmet shell, such dies being brought and maintained together withsubstantial pressure while the bonding fluid solidifies or dries orotherwise sets to at'least a sufiicient extent to maintain the integrityof the assembly when the dies are removed. Pressing the outer layerstogether against the impregnated central layers 132, 134 in this fashionnot only causes the fiutfed fibers of the layers 132 to becomeintertwined with the fabric 134, as apparent in Fig. 3, but also forcesout any air that may be trapped in these layers, and finally causes thebonding fluid to flow into the outermost layers 130, 136, filling thevoids in the latter.

While the operation has been described as involving the assembly of thewoven fabric 134 over the fluffed material 132, it will be understoodthat the flutfed material may alternatively be placed over the wovenfabric, or the latter may be disposed between two like, thinner layersof the flutfed material. In any case, the purpose and result of thearrangement is that the fibers 132 tend to pass through the intersticesof the fabric 134, filling them and providing an essentially continuousfiber mass which is reinforced by the woven net or textile 134 but whichhas a substantial fibrous structure in and around all of the openings ofthe fabric 134.

The bonding fluid not only permeates all 'of the composite inner fibrousmass constituted by the elements 132 and 134, but also the outer layers130 and 136 so that a single, unified or essentially monolithicstructure is provided. After the pressing operation has been completedand the bonding fiuid has dried or set to a solid state, the assemblybecomes an essential rigid but remarkably strong, plate-like structure.A particular feature of the arrangement is that unlike shell materialsmade by plastic impregnation of close-woven fabric bases, the completestructure has no linear grain or other predetermined lines of crackingor cleavage, yet is fully as tough and durable by reason of thereinforcement of the fabric 134 as well as by the intermeshed nature ofthe other fibrous materials, particularly the flutfed fibers 132traversing the openings of the material 134.

' The bonding medium may alternatively be applied after all layers havebeen assembled, although the insertion of such material at least priorto addition of the outermost or uppermost layer is believed desirablefor maximum insurance against entrapment of air. The bonding meany ofvarious plastic or like compositions, either of thermoplastic orthermosetting type, or of the type which can be liquefied by solution ina volatile liquid. Low pressure molding compositions have been foundespecially suitable. For instance, excellent products have been obtainedwith polyester resins, compounded and molded in known ways suitable toyield tough, rigid (or for some purposes very slightly or rigidlyresilient) bodies having good dimensional stability. Examples of thesethermosetting substances are the so-called polyester Selectrons (made byPittsburgh Plate Glass); thus a mixture of 49% of each PolyesterSelectrons 5003 and 5208 with 2% of an organic peroxide material such asLuperco ATC (made by Novadel-Agene) has yielded satisfactory hardcrownedhelmet shells. Variations in hardness or flexibility (e. g. when thecheck or car flaps are to be more or less flexible thanthe crown) areobtainable by suitable variation in proportions. Another kind of plasticsubstance especially useful for helmet shells of the impregnatedfibrous-base type comprises phenolic compositions, for example variousknown low pressure molding materials of such composition. As stated, thefibers of the various layers can be of various substances, glass fiberbeing at present preferred, but other natural or synthetic fibers beingalso useful, including asbestos, mineral wool, wood fibers as well asothers mentioned above. The fibers for the several layers may be allalike or may be of mutually different substances, it now beingunderstood that the nature of the bonding medium as well asthe fiberscan be selected to suit the circumstances under which the ultimatestructure is to give service.

While the composite material, thus composed of inter bonded fiber layerspermeated with a solidified plastic substance so as to constitute anessentially smoothsurfaced sheet, has been described as for constructionof the helmet shell 20, this type of sheet or plate-like material may beused for the manufacture of other devices, such as boxes, containers orthe like or may be used in panels or other shapes as parts of objects tobe assembled. The procedure and product are conveniently adapted formanufacture by a pre-mold operation, e. g. as between dies mutuallyshaped to fit the configuration of the desired helmet shell or otherstructure. Alternately, if the material is made for sheets'or panels,the bonding and pressing operations may be effected by passing itbetween rolls or the like. It will now be seen that the resultingarticle, for example the helmet shell 20, is rigid, tough and remarkablydurable. Furthermore, it has no grain in any predetermined direction andconsequently has no tendency to crack or split along predeterminedthread lines or the like, as characterizes ordinary impregnated fabricswhen struck by a sharp, heavy blow. The resistance to penetration onimpact has been found to be very high, as likewise the resistance tochipping, cracking, appreciable bending or the like.

The thickness, weight and rigidity of the plate-like composition can bevaried by altering the number or the thickness of the layers or plies.For example, the open weave fabric 134, or some of the soft, tluffedfibers of the mat 132, or both, can be omitted at the rear flaps 121 ofthe helmet so as to make these flaps more flexible in the finishedstate.

We claim:

A method of making a plate-like article, comprising assembling a woventextile reinforcing layer having substantial strength in face-to-facecontact with a slightly felted mat layer of relatively loose, fluifedglass fibers, said woven layer having meshes at least of the order ofone-sixteenth inch across so that said flutfed fibers tend to penetratesaid meshes, fastening the layers together only by compressing theassembly to intertwine the fluffed fibers with the open-weave textile,impregnating the assembly of layers with plastic bonding material, andsolidifying the plastic bonding material so that the structure comprisesan essentially integral plate-like article permeated throughout withsaid plastic bonding material.

References Cited in the file of this patent UNITED STATES PATENTS

